Protection against infections acquired through the mucosal surfaces of the genital tract can be achieved by the acquisition of strong local immunity. In human female and male genital tracts, antibodies (Abs) are locally produced, as well as plasma-derived. Based on this dual origin, one can assume that specific Abs can be induced either by systemic or mucosal immunizations. However, results of our previous immunization studies indicate that only low levels of Abs can be achieved in the human genital tract by systemic, oral, or rectal routes. In contrast, intranasal (IN) immunization of experimental animals resulted in disseminated mucosal (particularly strong in the genital tract), as well as circulatory responses. Our goal is to determine whether the results generated in the experimental animals can be validated in humans. We hypothesize that: 1. Generation of strong immune responses in the human genital tract can be accomplished by IN immunization;and 2. This route will be more efficient than the parenteral or other mucosal routes of vaccination, due to the preferential "homing" migration of antigen-activated cells to the genital tissues. To address this, we propose to immunize female and male human volunteers with a model antigen, influenza virus that, although not relevant for the genital tract infections, is the only commercially available vaccine for nasal application and is also obtainable in an injectable form. To evaluate the effectiveness of IN immunization for genital tract immunity, we propose to: 1. Determine and characterize the immune responses induced in human female and male genital tracts by the IN vs. the parenteral vaccination. The local and circulatory contribution to the induced responses will be determined by quantitative and qualitative analysis of Abs in the genital tract secretions, compared to sera and other external secretions (saliva;nasal and rectal lavages). We will determine: levels and relative proportion of Ab isotypes (particularly of IgA and IgG subclasses), the molecular forms of IgA (S-IgA, mIgA and pIgA), and the capacity of Abs to neutralize influenza virus. 2. Determine whether IN, compared to intramuscular immunization, will favor the migration of vaccine-sensitized cells to the genital tract to generate local responses. Specifically, we will compare the function of peripheral blood cells, expressing homing receptors for preferential homing to the genital tract ([unreadable]4[unreadable]1 integrin) or to secondary lymphoid tissues (L-selectin), with respect to the secretion of influenza virus-specific Abs and production of IFN-[unreadable]. The results of these studies will contribute to the understanding of the origin and the induction of immune responses in the human genital tract. This information will be useful for the design of effective vaccination strategies against sexually transmitted diseases, including HIV. Our goal is to demonstrate whether efficient, vaccine-specific responses in the human male and female genital tract can be achieved by intranasal immunization (compared to intramuscular), and how this relates to the homing pattern of vaccine-sensitized cells. The results obtained will be important for the design of immunization strategies to prevent infections with agents of sexually transmitted diseases.